Laminate flooring usually consists of a core of a 7 8 mm fiberboard, a 0.2 0.8 mm thick upper decorative surface layer of laminate and a 0.1 0.6 mm thick lower balancing layer of laminate, plastic, paper or like material. The surface layer provides appearance and durability to the floorboards. The core provides stability and helps, together with the surface layer, to give the floorboard sufficient impact strength. The balancing layer keeps the board plane when the relative humidity (RH) varies during the year. The floorboards are laid floating, i.e. without gluing, on the subfloor. Traditional hard floorboards in floating flooring of this type are usually joined by means of glued tongue-and-groove joints (i.e. joints involving a tongue on one floorboard and a tongue groove on an adjoining floorboard) on long side and short side.
In addition to such traditional floors, which are joined by means of glued tongue-and-groove joints, floorboards have recently been developed which do not require the use of glue and instead are joined mechanically by means of so-called mechanical locking systems. These systems comprise locking means which lock the boards horizontally and vertically. The mechanical locking systems are usually formed by machining of the core of the board. Alternatively, parts of the locking system can be formed of a separate material, such as aluminum, which is integrated with the floorboard, i.e. joined with the floorboard in connection with the manufacture thereof.
The main advantages of floating floors with mechanical locking systems are that they can easily and quickly by laid by various combinations of inward angling and snapping-in. They can also easily be taken up again and used once more at a different location. A further advantage of the mechanical locking systems is that the edge portions of the floorboards can be made of materials which need not have good gluing properties.
Laminate flooring and also many other floorings with a surface layer of plastic, wood, veneer, cork and the like are made by the surface layer and the balancing layer being applied to a core material.
The first generation laminate flooring, so-called HPL flooring, was made by providing a 6 mm thick particle board with a 0.8 mm surface layer of decorative high pressure laminate, usually referred to as HPL. HPL is made in a separate operation where a plurality of impregnated sheets of paper is compressed under high pressure and at a high temperature to a laminate board.
Later the second generation laminate flooring was developed, which is based on a more modern principle where both manufacture of the decorative laminate layer and the fastening to the fiberboard take place in one and the same manufacturing step. Impregnated sheets of paper are applied directly to the board and pressed together under pressure and heat without any gluing. As a rule, the surface layer is about 0.2 mm thick. This direct laminated flooring, usually referred to as DL flooring, whose main advantage is that the production cost is lower, was first inferior to HPL flooring owing to, inter alia, a lower degree of impact strength and lower moisture resistance. The quality properties of the DL flooring, however, were significantly improved when the particle board was replaced by a qualified HDF type fiberboard—high density fiberboard. The HDF board was considerably harder than the particle board and more resistant to moisture. Thus, the impact strength and moisture resistance of the DL flooring could be improved. As this HDF board was also being manufactured in increasingly larger volumes, the cost was reduced and DL flooring with an HDF core became number one on the market. Although the particle board is considerably cheaper than HDF, the DL technology combined with HDF is altogether less expensive. DL flooring now had quality properties equivalent to those of HPL flooring but was at the same time essentially less expensive.
At this time when DL flooring was being sold in larger quantities than HPL flooring, the laminate flooring was joined using a traditional locking system consisting of tongue, groove and glue. HPL flooring with a core of particle board was easier to glue than DL flooring with a core of HDF. When the mechanical joint systems were developed, also this problem was eliminated, and in a short time DL flooring with a core of HDF captured 90% of the market.
In addition to the above two methods, a number of other methods are used to manufacture floating floors and provide different core materials with a surface layer. A decorative pattern can be printed on the surface of the core, which is then, for example, coated with a wear layer. The core can also be provided with a surface layer of wood, veneer, decorative paper or plastic sheeting, and these materials can then be coated with a wear layer.
As a rule, the above methods result in a floor element in the form of a large board which is then sawn into, for instance, some ten floor panels, which are then machined to floorboards.
In all cases, the above floor panels are individually machined along their edges to floorboards. The machining of the edges is carried out in advanced milling machines where the floor panel is exactly positioned between one or more chains and bands mounted, so that the floor panel can be moved at high speed and with great accuracy past a number of milling motors, which are provided with diamond cutting tools or metal cutting tools, which machine the edge of the floor panel. By using several milling motors operating at different angles, advanced joint geometries can be formed at speeds exceeding 100 m/min and with an accuracy of 0.02 mm. JP-20011329681 discloses a floorboard having a multilayer core and a surface layer comprising wood veneer and a vapor proof layer arranged between the veneer and the core. The core comprises a middle layer of plywood and upper and lower layers of MDF.